1. Field of the Invention
The present invention relates to the support structure for a movable contact piece of a seesaw switch which performs a switching operation by rocking the movable contact piece.
2. Description of the Related Art
A seesaw switch which performs a switching operation by rocking a movable contact piece is widely used as a power window switch or a power seat switch of an automobile and so on. FIGS. 6 and 7 illustrate the support structures of the movable contact pieces in conventional seesaw switches. A movable contact piece 1 shown in FIG. 6 is bent at its center and symmetrically formed in the shape of the letter V. One of inclined portions 1a of the movable contact piece 1 is formed with slits 2. On the other hand, a guide strip 3 is provided to project upward from an inside bottom of a case of the switch. A slit 5a having a width longer than the distance between the slits 2 of the movable contact piece 1 is formed by press working in the center of the leading end of the guide strip 3, and projections 5b and 5b are formed on both ends of the leading end of the guide strip 3 by the slit 5a. In the seesaw switch having the support structure shown in FIG. 6, the movable contact piece 1 rocks on the leading end of the guide strip 3 serving as a fulcrum while the projections 5b of the guide strip 3 are engaged with the slits 2 of the movable contact piece 1, respectively. The movable contact piece 1 is positioned in its longitudinal direction by the engagement of the slits 2 and 2 and the projections 5b, and a switching operation is performed by the contacting and separation of an unillustrated fixed contact and the movable contact piece 1.
In the support structure of a movable contact piece 1 shown in FIG. 7, engaging strips 6 extend from both sides in the center of the movable contact piece 1 to project outward. On the other hand, concave portions 8 are formed on both side walls 7 of the case of the switch. As shown in FIG. 7, while the engaging strips 6 of the movable contact piece 1 are fitted in the concave portions 8 on the side walls 7 and the movable contact piece 1 is positioned in its longitudinal direction, the movable contact piece 1 rocks on a central terminal 10 which projects deviating slightly from the center of the movable contact piece 1, and a switching operation is performed by the contacting and separation of an unillustrated fixed contact and the movable contact piece 1.
The structures of the movable contact pieces 1 shown in FIGS. 6 and 7 are formed by press working. Slits 2, slit 5a, and engaging strips 6 are formed by breaking out sections of material. The slide between the slits 2 of the movable contact piece 1 and the slit 5a of the guide strip 3, or the slide between the engaging strips 6 of the movable contact piece 1 and the concave portions 8 of the side walls 7 is performed through broken-out sections formed by press working. Burrs on the broken-out section may prevent the slide from being stably performed, resulting in unstable rocking. Furthermore, the burrs also cause abrasions, and thus there is a problem with respect to the durability of the switch.